4.3 Example

This example uses a simple object named book that holds an author name and a book title:

class book 
{
   public:
     book ();
     book (const RWCString& title, const RWCString& author);
   private:
     RWCString title_;
     RWCString author_;
};

As described in the example in Chapter 3, you must add macros to the header and implementation files to prepare the object for serialization.

• To the header file, add the macro RW_DECLARE_VIRTUAL_STREAM_FNS(), which defines the streamContents() member function:

class book 
{
   RW_DECLARE_VIRTUAL_STREAM_FNS(book)

   public:
     book ();
     book (const RWCString& title, const RWCString& author);

   private:
     RWCString title_;
     RWCString author_;
};
Add to the header file:
            // Add serialization support 
        RW_DECLARE_STREAMABLE_AS_SELF(book)
        RW_DECLARE_STREAMABLE_POINTER(book)

• To the implementation file, first add macros that define insertion and extraction operators for the class members:

// Define how book will be serialized
RW_BEGIN_STREAM_CONTENTS(book)
   RW_STREAM_ATTR_MEMBER(title,title_)
   RW_STREAM_ATTR_MEMBER(author,author_)
RW_END_STREAM_CONTENTS

Then add macros that allow the book object itself to be serialized as a pointer reference:

// Allow a reference to a book to be serialized         
RW_DEFINE_STREAMABLE_POINTER(book)
RW_DEFINE_STREAMABLE_AS_SELF(book)

Now you are ready to look at the example itself.

This section explains the main() function for the example. The explanation is broken into three parts:

• creating a book object and serializing it to a file using an enhanced XML output stream

• reading the file back in and restoring the book object using an enhanced XML input stream

• printing out both the basic XML streams data for the book object and its more readable, enhanced XML stream version

For the complete example, see:

buildspace\examples\xmlstreams\xsltTransform\enhanced.cpp

First create a book object and serialize it out to a file. Because the XML format generated by XML streams is difficult to read, transform the output stream to a more easily-readable format.

int main()
{
   using std::ofstream;                                         //1
   using std::ifstream;
   using std::cout;
   using std::endl;

   book book1("To Love and Be Wise","Josephine Tey");           //2
   book book2;

   {
     ofstream fout("book.xml");                                 //3

     RWObjectOutputStream out =                                 //4
       RWEnhancedXmlObjectOutputStreamImp::make(fout);
     out << book1;                                              //5

   }

At this point you have written the book object XML data to the file book.xml. Next restore the object, which involves:

• reading in the file book.xml

• restoring the object as book2

   {
     ifstream fin("book.xml");                                  //1

     RWObjectInputStream in =                                   //2
       RWEnhancedXmlObjectInputStreamImp::make(fin);
     in >> book2;                                               //3
   }

Finally, the example writes to standard out two forms of the serialized object. You'll also use the rwInsertWithName() global method in order to provide an instance name for the book object.

   {
     RWObjectOutputStream out =                                 //1
       RWEnhancedXmlObjectOutputStreamImp::make(cout);
         out << rwInsertWithName("book2",book2);                //2
   }
   cout << endl;
   {
     RWObjectOutputStream out =                                 //3
       RWXmlObjectOutputStreamImp::make(cout);
     out << rwInsertWithName("book2",book2);                    //4
   }
   return 0;
}

Here is the resulting output:

In enhanced XML stream format:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<book2
xmlns:rw="http://www.roguewave.com/xmlstream" rw:class="book" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance">
xsi:type="rw:nested_object">
  <title xsi:type="xsd:string">To Love and Be Wise</title>
  <author xsi:type="xsd:string">Josephine Tey</author>
</book2>

In ordinary XML stream format:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  <rw:nested_object rw:name="book2" rw:class="book" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
  xmlns:rw="http://www.roguewave.com/xmlstream">
    <rw:member rw:name="title" xsi:type="xsd:string">To Love and Be
        Wise</rw:member>
    <rw:member rw:name="author" xsi:type="xsd:string">Josephine
        Tey</rw:member></rw:nested_object>

If you need to control the format of the data within the XML stream, the streams classes have a make() function that takes a pointer reference to an std::ios object. The constructor for the XML stream fills this pointer with the address of a formatting object for the underlying character stream. Here is an example for the class RWEnhancedXmlObjectOutputStreamImp.

std::ios* formatter;            // uninitialized pointer
RWObjectOutputStream xostr =   
        RWEnhancedXMLObjectOutputStreamImp::make(
        outfile,script,formatter);
formatter->precision(15);       // manipulate data format

The following classes contain a make() function that supports a formatting object:

• RWXmlObjectInputStreamImp

• RWXmlObjectOutputStreamImp

• RWEnhancedXmlObjectInputStreamImp

• RWEnhancedXmlObjectOutputStreamImp

• RWTTransformObjectInputStreamImp

• RWTTransformObjectOutputStreamImp

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